1. The Field of the Invention
The present invention pertains generally to the field of oil well cementing equipment, and more specifically to the cement head apparatus used in a sub sea cementing operation.
2. Description of the Prior Art
Traditionally, in the oil field industry, the rubber darts and/or rubber balls used for a down hole cementing operation are held in a cementing head, up and out of the cement slurry flow path. The rubber darts and/or balls are released at the appropriate time to join into the cement flow moving down the hole.
In many of the early designs, such as in U.S. Pat. No. 3,616,850, the dart simply falls into the flow path, while Bode in U.S. Pat. No. 5,095,988, uses pushers to inject the balls or darts into the flow. In order to guarantee plug passage, a wash-down manifold with two valves is often used with a dart containing cement head to redirect the flow from below to above the dart ensuring that it be washed down the hole.
In his patent U.S. Pat. No. 4,995,457, Baldridge adapts this design with a lift-through type cement head and a heavy-duty swivel to afford drill string lifting and rotation along with the release of a ball and a dart for sub sea cementing.
This system is awkward to handle and it requires that the drill string be rotated from below the swivel through the kelly by the rotary table.
My previous design in U.S. Pat. No. 5,950,724, provided a sub sea cementing head connecting directly below the top drive power drilling swivel, rated at 500 metric tons lifting capacity combined with 10,000 psi internal pressure and 50 rpm rotation speed. In this flow through design, the rubber dart is held in the middle of the slurry flow, protected in a cage. The ball is held within the sidewall. The mechanical ball dropper and dart release pin puller protrude out from the cement head. These devices maybe made remote control hydraulic, but this system is limited when dropping multiple darts or balls.
In sub sea well drilling applications performed by an off-shore drilling platform or specialized drill boat, the pipe lifting system has the ability to lift 750 metric tons or (1,653,450 lbs) of pipe. A cement head combines this load simultaneously with an internal 10,000 psi working pressure and has the ability to rotate at 50 rpm to assure sufficient displacement of the cement flowing around the casing being held below the drill pipe, and further to have flow capacity of up to 60 barrels per minute of cement flow at speeds of up to 50 feet per second.
Now therefore, there is a strong desire for a cement head in which, cement flows into the head from the top, and further has a high tensile strength and the capacity of swivel, and a reservoir for three balls or plugs or darts while maintaining fluid circulation, and further to release the staging elements by remote control.
The present invention is directed to a lifting cement head which is connected directly to the top drive power swivel, such that it carry the extreme high tensile load including the entire drill string. This cement head has the capacity to lift the entire drill string, of up to 750 metric tons or 1,650,000 lbs in combination with 10,000 PSI internal pressure. A further feature of the invention is a fluid swivel allowing drilling fluid or cement slurry to flow directly into the cement head central bore from an outside anchored connection, such that the drill string may be simultaneously rotated at 50 rpm. Accordingly, it is another object of the present invention to hold the rubber elements used in cementing in a multi celled reservoir cylinder, protecting them from the abrasive fluid circulated.
To these ends, a lifting top drive cementing head of the present invention, comprises a complete hydraulic remote control system to unlock, index the multi celled reservoir cylinder, and relock it. This system may also be manually over-ridden, to cycle it from the outside in the event of a hydraulic failure. It is yet a further object of this present invention to provide a mechanical outside position indicator of the rotating reservoir cylinder, and yet to disclose a lever style tattle tale device in the lower sub to indicate the dart passage down hole.
A lifting top drive cement head of the instant invention fulfills all of the above objectives. Further, a cement head of the present invention can be connected directly to the drilling swivel of the very largest offshore oil drilling rigs in the world today.
These and other objects, features, aspects, and advantages of the present invention will become better understood with reference to the following description and accompanying drawings.